This invention relates to the field of processing equipment for the fabrication of an integrated circuit.
In the fabrication of integrated circuits, a semiconductor wafer is subjected to many deposition steps. In some cases, a single deposition chamber with a single station many not have a sufficiently high run-rate to deposit a particular layer for a fabrication line. Multiple chambers can be used, for instance, each of which includes a chemical vapor deposition (CVD) stations for depositing a particular layer of dielectric on the wafers. When multiple chambers are used for a given layer, the chambers must be carefully balanced so that each provides the same film thickness. Otherwise the performance of some wafers may be different than others because some wafers will have thicker layers than others. This also is true where multiple stations are used in a single chamber and the entire thickness of a given layer is deposited at each station.
One class of equipment eliminates the need for balancing each station. This equipment uses several stations in the same chamber to sequentially complete a single deposition step by doing part of the step at each station. For instance, a layer may be deposited at four stations where one-fourth the total thickness of the layer is deposited at each of the four stations. All stations operate simultaneously on different wafers with each wafer being passed from one station to the next. This is akin to a serial production line and results in a run-rate approaching what can be achieved by having multiple chamber with single stations. One such deposition chamber with multiple stations is manufactured by Novellus and sold under the trademark xe2x80x9cVector.xe2x80x9d A problem associated with this multiple station chamber is discussed in the detailed description which follows along with the solution provided by embodiments of the present invention.